ADU rules in San Clemente

Detached ADUs are allowed on any lot with an existing or proposed home in every residential zone (Table 17.32.030 lists Accessory Dwelling Units as P in RVL, RL, RML, RM and RH), in mixed-use zones, and in commercial zones where the Housing Overlay or state law authorizes housing, subject only to a building permit (SCMC 17.28.270.C). On a single-family lot the city allows one detached new-construction ADU and one detached accessory structure converted to an ADU, in combination with an attached ADU and a JADU (D.1 to D.3, D.6); on a lot with an existing multifamily building it allows up to eight detached ADUs, never more than the existing units, and two beside a proposed multifamily building (D.4). Units built under the state-exempt pathway of Gov. Code 66323, such as an 800 sq ft detached unit with 4 ft side and rear setbacks, must be approved without conflicting local standards (J). Inside the coastal zone, which generally runs inland to Interstate 5, a detached ADU also needs approval from the California Coastal Commission, because the city has no certified Implementation Plan, and the Coastal Zone overlay's bluff, canyon and beachfront setbacks apply to local-track units (17.56.050).

One attached ADU is allowed on a lot with an existing or proposed single-family home, either inside the home's existing or proposed space or an attached accessory structure (with up to 150 sq ft of expansion for ingress and egress) or as attached new construction, provided it has exterior access and side and rear setbacks sufficient for fire safety (SCMC 17.28.270.D.1). One JADU of up to 500 sq ft may be created within or attached to a proposed or existing single-family home, with independent exterior access, in addition to an ADU, but not on a multifamily lot (D.6); the Ord. 1810 definition counts an attached garage as part of the home (17.88.030). On an existing multifamily lot, non-livable space such as storage rooms, attics, basements or garages may be converted into at least one ADU and up to 25 percent of the existing units (D.5). Attached and internal ADUs follow the height limit of the underlying zone (E.3.a-b). Inside the coastal zone the city's ADU page and packet require Coastal Commission approval for any ADU before city permits proceed.

Ord. 1810 caps a new detached or attached ADU at 850 sq ft of interior livable space for a studio or one-bedroom unit and 1,000 sq ft for two or more bedrooms (SCMC 17.28.270.E.4.a), the same figures as the Gov. Code 66321(b)(2) floor, and it dropped the percent-based size limit of former subsection F.4.b (the city's June 2026 packet still prints a 50 percent of living area cap for attached units). Zone setbacks, floor area limits, open space and site coverage may shrink an ADU but never below 800 sq ft of interior livable space where no alternative exists (E.4.c), and non-livable basement space is excluded from floor area (E.5). The caps do not apply to a conversion of existing space in the home or an existing accessory structure (E.4.b), and a JADU may be up to 500 sq ft (E.4.d). A detached ADU may be 16 ft tall, 18 ft on a lot with a multistory multifamily building or within one-half mile walking distance of a major transit stop or high-quality transit corridor (plus 2 ft to match the main roof pitch), and two stories within the zone height when built over a detached garage; attached and internal ADUs follow the zone height (E.3). Units built under Gov. Code 66323 follow the state standards instead (J): the single-family detached unit may be held to 800 sq ft with 4 ft setbacks, and 66323(a)(4) authorizes only height and setback limits for detached units beside multifamily buildings.

No owner has to live on a property with an ADU: Ord. 1810 deleted the clause, flagged in HCD's 10-14-2025 findings, that required owner occupancy for ADUs built after 1-1-2025, and Gov. Code 66315 bars such conditions. For a JADU, the owner must live in the main home or the JADU only when the JADU shares sanitation facilities with the home; if the JADU has its own bathroom, no owner occupancy is required (SCMC 17.28.270.G.3), matching Gov. Code 66333(b) as amended by AB 1154. A JADU still needs a recorded deed restriction that bars separate sale and fixes its size and attributes (G.4). The city's ADU information packet (created 6-4-2026) and its JADU deed restriction template still say the owner must live on site whenever there is a JADU; the code and 66333(b) control.

Each ADU needs one off-street space, which may be tandem or on an existing driveway (SCMC 17.28.270.E.9.a-b), unless an exemption applies: none is required for a JADU, an ADU inside a proposed home or converted from existing space of the home or an accessory structure, an ADU within one-half mile walking distance of public transit, one within a state-defined historic district or the city's Architectural overlay, where on-street permits are required but not offered, or within one block of a car-share vehicle (E.9.c.i-vi). Ord. 1810 defines public transit to include bus and trolley stops, train stations and SC Rides pickup locations (17.88.030); SC Rides is the city's discounted Lyft service, whose eligible pickups lie within 0.25 mile of the former OCTA bus routes 191 and 193, so the transit exemption reaches broad corridors of the city. Two exemptions apply only outside the coastal zone: no space for an ADU built together with a new home, and no replacement of a garage, carport or covered space demolished or converted for the ADU (E.9.c.vii-viii); staff summarized this as 'Replacement parking may only be required in the Coastal Zone.' State law bars both requirements (Gov. Code 66322(a)(6), which applies 'notwithstanding any other law', and 66314(d)(11)), so the coastal carve-outs lean on the Coastal Act savings clause of 66329(a), which preserves the Coastal Commission's own permit review rather than city zoning. The flat one-space rule also reaches studios, while 66314(d)(10)(A) caps parking at one space per unit or per bedroom, whichever is less, and units built under Gov. Code 66323 carry no parking (J; 66323(b)).

Conforming ADUs and JADUs are approved ministerially with a building permit in any residential or mixed-use zone (SCMC 17.28.270.C), and the city commits to the state review rules of Gov. Code 66317 and 66335 (K): a completeness determination within 15 business days and a decision within 60 days, with no hearing. Discretionary review (a Development Permit, or a Cultural Heritage Permit on a historic site) is reserved for ADUs that seek to vary from the 17.28.270 standards where state law allows discretion (Table 17.16.100; 17.16.110), and ADUs on historically significant properties are approved ministerially, with the Secretary of the Interior Standards applying only to properties on the State or National Register (H). Inside the coastal zone the city has no certified Implementation Plan, so after a city 'in-concept' review the applicant must obtain Coastal Commission approval before city permits proceed (city ADU page and packet). Gov. Code 66329(b) requires the Commission to approve or deny an ADU coastal permit within 60 days of a complete application, concurrently with the city's 66317 review, or the application is deemed approved, and requires the city to notify the Commission immediately when the ADU application is complete.

Ord. 1810 lets an ADU or JADU be rented but bars renting it 'for periods of 30 days or less' (SCMC 17.28.270.G.2), so the minimum term is 31 days: that matches the longer-than-30-days rule state law sets for JADUs and 66323 units (Gov. Code 66333(g), 66323(e)) and is one day stricter than the 30-day term 66315 lets a city require of other ADUs. The same rule keeps ADUs and JADUs out of the city's short-term lodging programs: STLUs (stays of 29 or fewer days, 17.88.030) are allowed only in the mapped STLU Allowed Areas of the RH, mixed-use and specific plan zones that list them, under a 20 percent cap, and STARs only in owner-occupied multifamily buildings by permit (17.28.292; Table 17.32.030), each with an annual operating license and the 10 percent transient occupancy tax; the city's ADU FAQ says short-term rentals such as Airbnb are not allowed with ADUs. No ADU or JADU may be sold or conveyed separately from the lot and main home except under Gov. Code 66341 (G.1), and San Clemente has not opted into the 66342 condominium conveyance.